Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$136.56	12.195%	$153.2135	$153.21	$153.20	$153.20
Purchase #2	$74.96	11.328%	$83.4515	$83.45	$83.45	$83.50
Purchase #3	$115.83	13.434%	$131.3906	$131.39	$131.40	$131.40
Purchase #4	$247.88	4.372%	$258.7173	$258.72	$258.70	$258.70
Purchase #5	$72.35	8.872%	$78.7689	$78.77	$78.75	$78.80
Purchase #6	$9.77	9.121%	$10.6611	$10.66	$10.65	$10.70
Purchase #7	$167.94	12.844%	$189.5102	$189.51	$189.50	$189.50
7 purchase totals =	$825.29		$905.7131	$905.71	$905.65	$905.80